Bigpond email on Mac Mail

Same issue as Glitch, I have had continued issues with being able to use bigpond email on the Mac mail - Th biggest issue is that I can receive but not send emails.

Periodically it works then just stop working. The last email I have received it 17 August. I can access my mail on my iPhone and ipad - just not my iMac. I followed the instructions given to Glitch but still not working.

I am not ready to use another client, I want this one to work - can you help me to get it to work please.